Configuration Items (CIs) that are within the scope of the plan are used by the Change Management process to evaluate and authorize changes. The Change Management process authorizes all changes on CIs which are within the scope of the SACM Plan.
So, while planning how to populate CMBD (which is in jurisdiction of Configuration management, or Service Asset and Configuration Management) you need to think about scope ("width" and "depth" of the implementation i.e. affected CI's), location, naming nomenclature, tools..etc. Once you define that i.e. have your plan ready, you can start the implementation. In scope of the planning you need to consider how (i.e. who, in which tool and with what authority) people involved in change Management will use information stored in CMDB.